Signaling system



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Aug. 26, 1941. J. wlcKs SIGNALING SYSTEM Filed oct. 31, 1958 5 Sheets-Sheet 5 k wmkm @WSG Q QML ESQ i SQ

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INVENTOR. f D hn Mick 5 BYM,M,M M407@ ATTORNEYS.

Patented Aug. 2s, 1941 2,253,743

SIGNAIING SYSTEM John wicks, oak Park, nl., assigner to Associated Electric Laboratories, Inc.. Chicago, Ill., a corporation of Delaware Application October 31, 1938, Serial N0. 237,891

B Claims.

ting up connections between the various lines of an automatic telephone system.

In a telephone system, apparatus is provided for the purpose of setting up a connection -between one line and any other line in the system which conventionally comprises iinder and connector switches having access to each line in the system and a number of intermediate traiiic concentrating switches interposed between the iinder and connector switches. In a small telephone system, intermediate traiiic concentrating switches are unnecessary and each finder and connector switch has access to each line in the system. In such a small telephone system, a finden 'switch' and a connector switch are arranged in a link, the iinder switch being operative to find a calling line in the system, and the connector switch being operative to select a desired called line in the system; and the call is routed between the calling and called lines by way of a link circuit extending between the finder and connector switches of the link. Various types of finder and connector switches for performing the functions noted are known in the art, one such type of switch being the so-called cross-bar switch. One of the best known and most successful forms of the cross-bar switch comprises first and second sets of movable bars arranged in intersecting relation, the first set oi bars individually corresponding to the groups of lines in the system and the second set of bars individually' corresponding to particular lines in each of the groups of lines in the system. A number of contact sets individually terminating the lines in the system are associated with the bars, each contact set being partially operative a under the control of a particular bar in each of the rst and second sets oi bars associated therewith and being fully operative under the joint control of the two associated bars. The construction and arrangement of the cross-bar switch is such that, when a particular bar in the rst set of bars is operated, the group of contact sets terminating the associated group of lines in the system is partially operated; and, when a particular bar in the second set of bars is operated, the group of contact sets terminating the associated and corresponding lines in the groups of lines is partially operated, only the contact set associated with both of these bars (Crus-2z) being fully operated. Thus, these operations or the two bars noted are effective to causev the switch to seize in the` group of lines corresponding to the first-mentioned Ybar the line' corresponding to the second-mentioned bar.

While the above-described type of cross-bar switch has met with some approval, it has not been generally accepted due to certain disadvantages in regard to the constructional and operational features thereof. More particularly, from the foregoing description of the construction and arrangement of this type of cross-bar switch, it will be apparent that only one call at any given time may be routed therethrough; and the cross-bar switch may be employed as the switching mechanism in only one finder or connector switch, two cross-bar switches being required in each nder-connector link in the sys- 20 tem. Hence, a relatively large number of such links are required in even a small telephone system if an adequate number of links are provided to render satisfactory services to the subscribers.

Accordingly, it is anobject of the present invention to provide, in a signaling System, improved unitary switching apparatus which is so constructed and arranged that it comprises both a finder switch and a selector switch.

Another object of the invention is to provide, in a signaling system, improved unitary switching apparatus which is so constructed and arranged that it comprises a plurality of finder and connector switches arranged in a number of finder-connector links in order to provide for the routing of co-existing calls through the switching apparatus.

A further object of the invention is to provide 40 improved switching apparatus of the cross-bar type which is of simple construction and arrangement and which is economical to manufacture and thoroughly reliable in operation.

The features of the present invention are illustrated as being incorporated in an automatic signaling or telephonesystem including a plurality of signal or subscriber lines, each line having a linef circuit individually associated therewith, and Kmeans including improved unitary switching apparatus of the cross-bar type for setting up connections between the various lines. The improvedswitching apparatus is so constructed and arranged that it comprises a number of finder and connector switches, each switch having access toeach line in the system.

The iindver and connector switches are arranged in links, each link including a link circuit provided with control and impulse responsive apparatus for governing the operations of the associated iinder and connector switches, respectively. SubscriberA substations are associated with the lines; and a distributor is provided for the purpose of assigning idle ones of the links to calling ones of the lines in a predetermined order.

In accordance with one feature of the invention, the unitary switching apparatus comprises a plurality ofv operating elements, each of the operating elements being associated with only one oi' the groups of lines in the system, a plurality of operating members, each of the operating members being associated with only one of the lines in the system, and means controlled by the joint operations of one of the operating elements and one of the operating members for selecting from the group of lines corresponding to the one operating element the line corresponding to the one operating member. More particularly, this switching apparatus comprises a plurality of divisions of operating elements, each of the divisions of operating elements being associated with only one of the groups of lines, whereby a particular line in a particular group of lines may be selected by the joint operation of any one of the operating elements in the division of operating elements corresponding to the group of lines including the particular line and the operating member corresponding tothe particular line. More specifically, the switching apparatus comprises a plurality of first and second operating elements arranged in divisions as previously noted, the i'lrst operating elements being operative in conjunction with the operating members to select calling lines, and the second operating elements being operative in conjunction with the operating members to select called lines. Corresponding ones of the rst operating elements in the divisions or rst operating elements are respectively associated with trunk lines extending to the link circuits from the switching apparatus; and corresponding ones o! the second operating elements in the divisions oi second operating elements are respectively associated with trunk lines extending from the link circuits to the switching apparatus, whereby a selected calling line may be connected to a trunk line extending to one of the link circuits and a selected called line may be connected to a trunk line extending from one of the link circuits.

In accordance with another feature of the invention, the distributor'associated with the switching apparatus is so connected and arranged that it is operative in response to the creation of a calling condition on one of the signal lines to cause the operations of one of the rst operating elements associated with a trunk line extending to an idle one of the link circuits and included in the one of the divisions of rst operating elements associated with the group of signal lines including the calling signal line and the one of the operating members associated with the calling signal line, thereby to seize the calling signal line and to connect the calling signal line to the trunk line extending to the one link circuit. Also, each one of the link circuits includes impulse responsive means forv selecting any one of the called signal lines and for testing the idle or busy condition of the selected called signal line, and means controlledby the last-mentioned means in the event the selected called signal line is tested idle for causing the one of the second operating elements associated with the trunk line extending from the one link circuit and included in the one of the divisions of second operating elements associated with the group of signal lines including the selected called signal line and the one of the operating members associated with the selected called signal line to be operated, thereby to seize the selected called signal line and to connect the seized called signal line to the trunk line extending from the one link circuit. Subsequently, the trunk lines extending to and from the one link circuit are connected together, thereby to interconnect the seized calling signal line and the seized called line for communication therebetween.

In accordance with a further feature of the invention, the switching apparatus comprises a plurality or groups of elementary switches, each group of elementary switches being associated with only one of the rst or second operating elements, and each elementary switch being associated with only one of the operating members. Each o! the elementary switches is so constructed and arranged that it is partially operative under the control of the operating element and under the control of the operating member associated therewith and is fully operative under the joint control of the associated operating element and operating member. More specifically, each of the elementary switches constitutes a circuit controlling device and comprises a flexible rst contact member mounted at one portion thereof and provided with an outwardly extending portion having a normal position and a second contact member having a normal position. The second contact member has a recess therein adapted to receive and engage the outwardly extending portions of the first contact member.

The operating element associated with the elementary switch is operative to flex the outwardly extending portion of the first contact member away from its normal position along a first path into the intersection of the first path and a second path; and the operating member associated with the elementary switch is operative to move the second contact member away from its normal position along the second path across the intersection of the rst and second paths. The elementary switch is so constructed and arranged that the recess in the second contact member receives and engages the outwardly extending portion of the rst contact member only in the event that the outwardly extending portion of the first contact member is disposed in the intersection or the first and second paths when the second contact member is moved thereacross and -that the outwardly extending portion of the rst contact member is ilexed along the second path when it is engaged by the second contact member. Also, the recess provided in the second contact member comprises means for restraining the outwardly extending portion of the first contact member in engagement with the second contact member under the control of the operating member associated with the elementary switch and until the second contact member is returned toward its normal position.

Further features oi' the invention pertain to the particular arrangement of the circuit elements of the system and to the particular construction and arrangement of the elements of the switching apparatus, whereby the above-outlined and additional featuresare attained.

'trate diagrammati'cally a telephone system incorporating a cross-.bar switch and embodying the present invention; Fig. 4 illustrates diagrammatically the general trunking arrangement of the telephone system shown in Figs. 1, 2 and 3, and the general construction and arrangement of the cross-bar switch incorporated in the telephone system and embodying the present invention; Figv 5 is a schematic illustrationy of a portion of the cross-bar switch further illustrating the construction and arrangement thereof; and Fig. 6 is a perspective view of one of the elementary switches included in the cross-bar switch shown in Fig. 5.

Referring now more particularly to Figs. 1 to 4,

inclusive, of the drawings, the telephone system there illustrated comprises an exchange having.

a plurality of subscriber lines including the subscriber lines and |2, terminating thereat, a cross-bar switch 50 therein and provided with a plurality of links, the first, ,second and third links being indicated, for setting up connections between the various subscriber lines. Also, a distributor is provided for assigning idle ones of the links to the use of calling ones of the lines. More specifically, the exchange has an ultimate capacity o f onel hundred lines and the number of links is determined by the amount of trailic which the exchange is required to handle, usually ten links being adequate to render satisfactory service.

constructed and arranged that it comprises a finder switch and a connector switch individually associated with each link and each switch having access to each line in the system; the first, second and third links have the finder switches 52 and 53 and the connector switches 50, 55 and 54 respectively associated therewith. Each finder switch comprises five portions respectively associated with the five groups of lines terminating at the exchange, each portion being provided with a group or FG" magnet operative to conditionany one of the twenty lines in the associated group of lines to be seized. Similarly, each connector switch comprises five portions respectively associated with the five groups of lines terminating at the exchange, each portion being provided with a group or CG 4magnet operative to condition any one of the twenty lines in the associated group of lines to be seized. Furthermore, the cross-bar switch comprises a plurality of line or L magnets individually associated with the lines terminating at the exchange, ea'ch of the L magnets being operative to cause the associated line to be seized by the finder or connector switch offone of the links in the yevent the group of lines including the associated line hasA been previously conditioned to be seized by the operation of the associated FG" or CG" magnet, respectively, therein, in amanner more fully explained subsequently. Also, each link is provided with control apparatus individually associated therewith, the control apparatus individually associated with the first, second and third links being respectively indicated at 200, and 202. y b

Each of the links may be identical to the first link illustrated, and the control apparatus individually associated with each link may be identical to the control apparatus 200 individually associated with the first link. Referring now more particularly to Figs. 1, 2 and 3, it will be observed that the first link comprises a iinder switch 5| and aconnector switch 56, each having access to each line in the system; and the control apparatus 200 `individually associated with the first link comprises a line relay R2l0, a hold relay R220, a back bridge relay R200, a ring cut-off relay R210, a busy relay R280, two transfer relays R230 and R240, two control relaysR2|5 and R250, a test relay R255, the control and controlled circuits associated therewith, and two minor switches 300 and 3|0. The minor switch 300 comprises two contact banks 302 and 300, respectively provided with contact wipers 30| and 303, a rotary magnet M305 for simultaneously rotating the two wipers 30| and 303 across the contacts in the associatedv contact banks, and a release magnet M305 for releasing these two wipers and for causing these two wipers to be returned to their normal positions. 'I'he minor switch 3|0 comprises twocontact banks 3| 2 and 3H, respectively provided with the contact wipers 3I| and 3| 3, a rotary magnet M3|5 for simultaneously rotating the two wipers 3|| and 3|3 across the contacts in the associated contact banks, and a release magnet M3|6 for releasing these two wipers and for causing these two wipers to be returned to their normal positions. Furthermore, two sets of switch springs S301 and S3| are respectively associated with Athe wipers of the minor switches 300 and 3|0,

and are actuated into engagement when the wipers of the associated minor switch are rotated away from their normal positions.

A subscriber substation is associated with each of the subscriber lines, the subscriber substations A and B being respectively associated with the subscriber lines and I2. Each, of the subscriber substations is provided with a telephone instrument, a dial mechanism, and a ringer. A line circuit is individually associated with each subscriber line in the system, the line circuit being individually associated with the subscriber line and the line circuit 360 being individually associated with the subscriber line I2. The line circuit |80 comprises a line relay R|60 and a cut-off relay Rl'l0; and the line circuit 360 comprises a line relay R350 and a cut-off relay R340. Furthermore, 'each of these line circuits is provided with control and controlled circuits associatedv with the relays therein. Preferably, the line circuits are of identical connection and arrangement.

'I'he distributor, |00 comprises ve group relays individually associated with the five groups.

of lines terminating at the exchange, the group relays R|00 and R||0, illustrated,being individually associated with the first and second groups of lines terminating at -the exchange, a relay individually associated with each link included in the system. the relays RIN, R|30 and 'lines terminating at the exchange.

R|40 being respectively associated with the iirst, second and third links, illustrated, included in the system, and a reset relay RI50. Furthermore, the distributor comprises control and controlled circuits associated withthe relays therein.

Referring now more particularly to Figs. 4 and 5 oi' the drawings, the cross-bar switch there illustrated and incorpora-ted in the telephone system, shown in Figs. 1, 2 and 3, comprises a number of finder switches 5|, 52, 53, etc., and a number of connector switches 56, 55, 54, etc., respectively included vin the first, second, third, etc., links. Each of the nder and connector '-switches includes ve portions, each portion having access to one of the groups of twenty Each portion of each of the finder switches is provided with an operating element or bar which is 0perated by an FG magnet individually associated therewith. For example, the first portions of thender switches 5|, 52 and 53 are provided with the operating elements IFGIS, AZFG'IS and 3FGIS, respectively, theseoperating 'elements being operated by the "FG" magnets IFGI, 2FG| and 3FGI, respectively, and lconstituting a division of first operating elements, and the first and second portions of the finder switch 5| are provided with the operating elements IFGIS and |FG2S, respectively, these operating elements being operated by the FG magnets |FG| and |FG2, respectively. Similarly, each portion of each of the connector switches is provided with an operating element which is operated by a CG magnet individually associated therewith. For example, the rst portions of the connector switches 56, 55 and 54 are provided with the operating elements ICGIS, 2CG|S and 3CGIS, respectively, these operating elements being operated by the CG magnets ICGI, 2CG| and 3CGI, respectively, and constituting a division of second operating elements; and the first and second portions of the first connector switch 56 are provided with the operating elements ICGIS and ICGZS, respectively, these operating elements being operated by the CG" magnets, ICGI and |CG2, respectively. Also, each operating element causes twenty elementary switches 600 associated therewith and included in the associated portion of the finder or connector switch to be partially operated. For example, the operating element IFGIS causes the twenty elementary switches 500 associated therewith and included in the associated first portion of' the finder switch 5| to be partially operated; and the operating element ICGIS causes the twenty elementary switches 600 associated therewith and included in the associatedrst portion of the connector switch 56 to be partially operated.

Furthermore, the cross-bar switch comprises a number of operating members or bars individually associated with the lines in the system, each operating member being operated by an L magnet individually associated therewith. For example, the operating members L|| S and LIZS are respectively associated with the lines and |2 and are operated by the L magnets Lil and L|2 respectively associated therewith. Also, each operating member causes a number of elementary switches 600, associated therewith and individually included in corresponding portions of each of the finder and connector switches, to be partially operated. For example,

Furthermore, it is noted that the twenty elementary switches 600 associated with each of the five operating elements in each iinder switch are multipled together and connected to a trunk line extending Vto the control apparatus associated with the link which includes the finder switch; and the twenty elementary switches 600 associated with each of the five operating elements in each connectorswitch are multipled together and connected to a trunk line extending from the control apparatus associated with thev link which includes the connector switch. For example, the twenty elementary switches 600 associated with each of the five operating elements in the finder switch 5| are multipled together and connected to the trunk line |05 extending to the control apparatus 200 associated with the first link; and the twenty elementary switches 600 associated with each of the five operating elements in the connector switch 54 are multipled together and connected to the trunk line-extending from the control apparatus 202 associated with the third link. Also, the

elementary switches associated with each of the operating members are multipled together and connected to the subscriber line associated therewith. For example, the elementary switches associated with the operating member LI IS are multipled together and connected to the subscriber line associated therewith. Furthermore, it is noted that an elementary switch in either a finder or,a connector switch is fully operated when it has been partially operated by both the operating element and the operating member with which it is associated, and when the elementary switch is fully operated it is eiective to connect a subscriber line to a trunk line extending to or from the control apparatus associated with one of the links. For example, the subscriber line is connected to the trunk line |05 extending to the control apparatus 200 associated with the first link when the operating element IFGI S and the operating member LHS are operated; and the subscriber line I2 is connected to the trunk line extending from the control apparatus 202 associated with the third link when the operating element 3CG|S and the operating member L|2S are operated. Finally, it is noted that, in fully operating one of the elementary switches 600, the FG or CG magnet with which it is associated is operated first, Aand then the "L" magnet with which it is associated is operated; and that the elementary switch 600 is retained in its operated position under the control of only the L magnet with which it is associated, the FG or CG magnet being restored after the L magnet is operated, as will be more fully explained subsequently.

Referring now more particularly to Fig. 6 of the drawings, one of the elementary switches 600 is shown in detail, and comprises three flexible contact rods 60|, 602, and 603 arranged in a horizontal plane disposed below three cooperating contact strips 604, 605 and 606, respectively associated therewith. The contact rods 60|, 602 and 603 are securely retained in place by two insulating members 601 and 606 between which the inner ends of the contact rods are firmly clamped.

Also, it is noted that the contact rods 60|, 602

, erated by each of the magnets 622 and 626, thereand 603 are arranged in spaced parallel relationship, these contact rods being retained int-this position by cooperating `ots 609 formed in the engaging faces of the insulating members 601 and 608. The contact stripsA 604, -606 and 606 are securelyy retained by a number of screws 6|0, 6II and 6I2, respectively, to an insulating member 6 I 3 which is carried by a movable strap I 4. Each of the contact strips is of substantially inverted L-shaped configuration, the forward end of the leg of the L being provided with a recess therein vwhich is adapted to receive theouter end of the contact rod associated therewith. The recesses provided in the forward ends of the legs of the contact strips 604, 605 and 606 are respectively shown at 6|5, 6|6 and 6|1.

The contact rods 60|, 602 and 603 are associated with a movable operating element or bar 6I8 which is disposed below the rods. Also, the operating element 6I8 is provided with an insulating plate 6I9 on its upper surface which is adapted to be moved into engagement with the contact rods 60|, 602 and 603. Also, the movable strap operating member or bar 62|. 'It is noted that the operating element 6I8 is movable in a vertical direction, whereas, the operating member 62| is movable in a direction transversely of the contact rods. The operating element 6I6 is operated by one of the FG or CG magnets 622, which comprises a field structure 623 to which the insulating members 601 and 608 are secured, a winding 624 and a movable armature 625 pivotally mounted upon the field structure 623 by a-pair of spaced apart pivot pins 626. Also the armature 625 is provided with a rearwardly extending flange 621 which directly engages the lower surface of the operating element 6I8. The operating member 62| is operated by one of the L magnets 628 which comprises a magnetic field structure provided with a winding 629 and a movable armature 630 associated therewith and secured to the operating member 62 In operating the elementary switch 600, the winding 624 of the magnet622 is first energized, thereby to cause the armature 625 thereof to be pivoted in a counter-clockwise direction, as viewed in Fig.'6, about the pivot pins 626. This movement of the armature 625 causes the flange 621 carried thereby to engage the operating element 6| 8 and move this element upwardly. This movement'of the operating element 6|8 fiexes the contact rods 60|, 602 and 603 upwardly and out of Ithe horizontal plane which they normally occupy, whereby the outer ends of these rods are positioned in alignment with the recesses 6 5, 6 I6 and 6I1, respectively, provided in the contact strips 604, 605 and 606, respectively. The winding 629 of the magnet 628 is then energized, thereby to cause the armature 630 to be attracted toward the eld structure thereof and the operating member 62| to be moved rearwardly, as viewed in 6. This movement of the operating member 62| causes the strip 6I4 carrying the contact strips 6I4 is secured by a screw 620 to a movable 25 604, 605 and 606 to be moved transversely by -to cause this elementary switch to be fully operated. AfterV theelemen-tary. switch 800 is fully operated, the magnet 622 maybe deenerglzed, thereby to causethe operating element 6|8 tovbe returned to its normal position without aecting theoperated positionof the elementary switch 600, .the 'contactrods 60|, 602 vand 603 being retained in their upwardly and rearwardly flexed positions under .the control of the operated magnet 628.

In order to release the elementary switch 600 the winding 629 of the magnet 628 is deenergized, whereupon thecontact rods 60|, 602 and 603 are moved forwardly, due to their resiliency; and the ends thereof are moved out of the recesses 6|5, 6|6 and 6|1 provided in the contact strips 604, 605 and 606, respectively, whereupon the contact rods are moved downwardly, due to their resiliency, to their normal positions.

Also it is noted that, in the event the winding 629 of the magnet 628 is energized prior lto the energization of the winding 624 of the magnet 622, the contact strips 604, 605 and 606 are moved transversely with respect to the contact rods 60|, 602 and 603 'and over the ou-ter ends of the contact rods without engagement therewith. Subsequently, if the winding 624 of the magnet 622 is energized, the contact rods 60 I, 602 and 603 are moved upwardly without engaging the contact strips 604, 605 and 606, respectively, due to the fact that the ends of the legs of the contact strips 604, 605 and 606 provided with Ithe recesses therein are slightly offset with respect to the stems of these contact strips. Thus, it will be apparent that, although the elementary switch is partially operated by both of the magnets 628 and 622, when the winding 629 of the magnet 628 is energized prior to the energization of the winding 624 of the magnet 622, no contact is'" established between the contact rods 60|, 602 and 603 and the respective contact strips 604, 605 and 606. At this time, the contact rods 60|, 602 and 603 are returned downwardly to their normal positions in response to the deenergization of the winding 624 of the magnet 622; similarly, the contact strips 604, 805 and 606 are returned forwardly to their normal positions in response to the deenergization of the winding 629 of the magnet 628. When the contact strips 604, 605 and 606 are returned forwardly to their normal positions under these conditions and prior to the time the contact rods 60| 602 and 603 are returned to their normal positions, the rear surfaces of the outer ends of the legs of these contact strips may contact the outer ends of the respective contact rods. However, there is no positive engagement therebetween and the contact strips are forced thereby forwardly to their normal positions.

From the foregoing it is apparent that the elementary switch 600 is partially operated when the winding 624 of the magnet 622 is energized and when the winding 629 of the magnet 628 is energized. Furthermore, it is noted that the elementary switch 600 is fully operated to establish a connection between the contact rods 60|, 602 and 603 and the contact strips 604, 605 and 606, respectively, only in the event that the winding 624 of the magnet 622 is energized prior of two ofthe elementary switches 000 for each link provided in the system are associated with the operating member 52|.

'I'he construction and arrangement of the elementary switch son is disclosed and claimed in f of to establish a connection between two of the lines in the system. For example, assuming that the subscriber line II is a calling line, the distributor I associated with the system causes a FG magnet associated with the group of twenty lines including the calling line II, and included in the finder switch of an idle one of the links, to be operated. Thus, one of. the "FG" magnets IFGI, ZFGI, etc., associated with the first group of lines including the calling line I I and included in the finder switches 5 I, 52, etc., respectively, of the first. second, etc., links, respectively, is energized. Assuming that the rst link is assigned by the distributor vto the use of the called line. the magnet I FGI associated with the first group of lines and included in the first portion of the finder switch I of the first link is energized, thereby to cause the operating element IFGIS associated therewith to operate partially the twenty elementary lswitches 600 asv sociated therewith. More particularly, the operating element IFGIS associated with the magnet IFGI flexes the contact rods included in the twenty elementary switches 000 associated therewith upwardly out of their normal positions. Subsequently, the distributor causes the magnet LII associated with the calling subscriber line II to be energized, whereupon the operating member LI IS associated therewith is operated. 'Ihis operation of` the operating member LI IS causes the contact strips of the elementary switches associated therewith and included in the first portion of the finder and connector switches to be moved transversely of the Acontact rods included in these elementary switches. From the foregoing description of the elementary switch 600, it will be apparent .that this movement of the contact strips of the elementary switches associated with the operating member LI IS will be effective to cause only the elementary switch 000 associated with both the operating element IFGIS and the operating member LIIS to be fully operated, thereby to connect the subscriber line I-I to the trunk line |05 extending to the control apparatus 2" associated with the first link. Subsequently, .the distributor causes the magnet IFGI to be deenergized, whereby the contact rods of each of the elementary switches 000 associated with the operating element IFGIS, with the exception of the contact rods in the fully operated elementary switch 600 associated with -both the operating element IFGIS and the operating member LIIS, are returned to their normal positions, the contact rods in the vfully operated elementary switch 000 being retained in their operated positions due to the fact that the operating member LI IS occupies its operated position under the control of the operated magnet LII.

Assuming that the subscriber line II is to be connected to the subscriber line I2, the control apparatus 200 associated with the first link is then operated under the control of the subscriber therewith to be energized. When the magnetv When the magnet ICGI is energized, the'operating element ICGIS associated therewith is operated, thereby to cause the contact rods of the twenty elementary switches associated therewith to be moved upwardly from their normal posltions. Subsequently, the control apparatus 200 associated with the first link tests the called subscriber line I2 and, in the event this subscriber line is idle, causes the magnet LI2 associated LI2 is thus energized, the operating member LI2S associated therewith is operated, thereby to cause the contact strips of the elementary switches-000 associated therewith to be moved transversely of the -contact rods included in these elementary switches. From the foregoing description of the operation of the elementary switchf500 it will be apparent that only the elementary switch 600 associated with both the operating element ICGIS and the operating member LI2S will be fully operated, thereby to establish a connection between the trunk line 252 extending from the control apparatus 200 associated with the rst link and the called subscriber line I2. Subsequently, the control apparatus 200 associated with the first link causes the magnet ICGI to be deenergized, thereby to cause the contact rods of each of the elementary switches 500 associated with the operating element ICGIS associated with this magnet, with the exception of the contact rods in the fully operated elementary switch 600 associated with both the operating element ICGIS and the operating member LI2S, to be returned to their normal positions, the contact rods in the fully operated elementary switch 500 being retained in their operated positions due to the fact that the operating member LI2S occupies its operated position under the control of the operated magnet LI2. Finally, the control apparatus 200 associated with the rst link operates to connect the trunk line |05 extending thereto from the cross-bar switch 50 to the trunk line 252 extending therefrom to the cross-bar switch 50, thereby to complete van established connection between thecalling subscriber line` II and the called subscriber line I2."

The release of this established connection is under the control of the control apparatus 200 associated with the first link, and this control apparatus is controlled to cause this established connection to be released by causing the windings of the magnets LII and LI2 to be deenergized. When the windings of the magnets LII and LI2 are deenergized, the operating members LI IS and LI 2S, respectively associated therewith, are returned to their normal positions, thereby to cause the contact st-ripsy of the elementary switches associated with each of these operating members to be returned to their normal positions, as previously explained.

Also it is noted that, while this established connection between' the calling subscriber line II and ghe called subscriber line I2 is completed, these wo connector switches there is no interference with twenty lines, including lower winding of RI to battery.

the completion of other calls from and to other subscriber lines in the system. For example. should a call be initiated on another line in the iirst group of lines at this time, the distributor I00 associated with the 'cross-bar switch I0 is operative to cause the second idle link to be assigned to the use `oi the calling subscriber line. whereupon the magnet ZFGI associated with the first group of twenty lines and included in the iirst portion of the finder switch i2 of the second link is energized, in a manner similar to that previously explained. When the winding of the magnet 2FGI is thus energized th'e operating element 2FGIS is operated, thereby to cause the contact rods of the twenty elementary switches associated therewith to be operated away from their normal positions, in the manner previously explained. At this time, although the contact strips of the elementary switches respectively asfsociated with the operating members LI IS and LI2S and associated with the operating element 2FGIS are operated, these elementary switches are not fully operated to cause the subscriber lines II and I2 to be connected to the trunk line extending from the cross-bar switch 50 to the control apparatus associated with the second link, due to the fact that the contact strips of these elementary switches were operated prior to the operation of the contact rods thereof. Thus, the established connection between the subscriber lines II and I2 is not interfered with in any way due to the subsequent operation oi the operating element IZFGIS. Moreover, this established connection between the subscriber lines II and I2 does not interfere, in any way, with the operation of the operatingelement 2FGI S in the first portion oi' the iinder switch 52 to seize the calling subscriber line in the rst group of twenty lines or the operation of the connector switch 55 of the second portion to seize a called subscriber line in the iirst or any other group of twenty lines in the system.

The connection and arrangement of the system will best be understood from a consideration oi' the following description, with reference to Figs. l, 2 and 3 of the drawings, of the detail operation of the apparatus incorporated therein to set up the different connections between the various subscriber lines.

For example, a call which is to be extended from the subscriber substation A to the subscriber substation B is iirst initiated at the substation A by removing the receiver of the telephone instrument thereat from its hook, thereby to complete a bridge path at the telephone instrument at the substation A between the line conductors CI00 and CI8I of the subscriber line II extending to the substation A. When this bridge path is completed between the line conductors ot the subscriber line "I I, a bridge circuit is completed for energizing the lower winding of the line relay RI60 in the line circuit |80 individually associated with the subscriber line II, which extends from ground', at IILA2, by way of IILCl, CI8I, the bridge path at the substation A between CIBI and CI80, CI80, IILAI, RAIII, RCIlI, and the When energized over the above-traced circuit the' line relay RI60 operates to complete, at RAIN, an obvious path for applying ground potential, at RAIII, to the start conductor CISG extending into the -distributor |00. It is noted that the start conducor CISG is multipled to the line circuits individually associated with the other subscriber lines in the tlrst group of twenty lines including the subscriber line Il. Thus, it will be apparent, when a call is initiated on any one of the subscriber lines included in the ilrst group of twenty lines, the line circuit individually associated with the Icalling line is operative to complete a path for applying ground potential to the start conductor CISG. In a similar manner, it will be understood that, when a callis initiated on a subscriber line ingfsubscriber line II, the line relay RI60 also prepares, at RAISE, a point in a circuit-traced hereinafter for energizing the cut-o relay RI10, prepares, atl RAI62 and RAI63, a point in a circuit traced hereinafter for energizing the upper winding of the line relay RI60 in series with the winding of the magnet LII individually associated with the subscriber line II. Finally, the line relay RI60 interrupts, at RAI63 and RCI,

a point in a chain ground circuit including the.

conductors CIBB, CIM and C334 extending through the line circuits associated with the subscriber lines in the iirst group of twenty' lines, thereby to prevent circuits for energizing the fL. magnets individually associated with theother subscriber lines in the iirst group of twenty lines and corresponding to the magnet LII irombeing completed prior to the completion -of the -p`reviously mentioned circuit for energizing in series I the upper winding oi' the line relay RI 6,0, andthe winding of the magnet LII. of the above-mentioned chain ground circuit-pre'-l vents more than one of the L magnets 'individually associated with the subscriber lines in the first group of lines from being simultancoi'lsly.

energized, 'thereby to prevent the cross-bar swi'tch 50 from operating and seizing two callingl'lines simultaneously.

Continuing now with the operation ofthe distributor VI00, when ground potential -is applied to the start conductor CISG an obvious circuit is completed for energizing the relay RI00 Vtherein; When thus energized, the relay R'I00 operates to condition, at RAI02, a chain circuit for energizeing the reset relay RI50 in the event the-dis# tributor |00 has previously operated to assign the last link therein to the use of a calling line. This chain circuit is completed from ground, 4at

RAZ, in the event the test relay R2 55.in the first link and the corresponding test relays in the other links are not operated atlthis time, and extends from ground, at RA250, by way of RC251, the chain circuit extending through the contacts controlled by the test relays in the' otherA links corresponding to the test relay R255' in the iirst link, CIQI, RAI02, RAIZI, RCI23,v RAI, RCI, RAI42, RCI, and the winding 'of .R'III to battery. When energized over the. abovetraced circuit the reset relay RIM operates. .toi

complete, at RAISI, a circuit for energizingthe relay Rl zo in the distributor loo in the event the.

irst link is idle, this circuit extending from ground, at RA226 by way of RC22'I, CI, RAIII, and the winding oi' RI 20 to battery. When energized over the above-traced circuit the relay This interruption i RI20 operates to complete, at RAIN, an obvious holding circuit for energizing the winding there- 'of extending from ground, at RA226, to battery atfthe winding of RI20. Also it isnoted that the reset relay R|50 completes, at RAIBI, RAIIS, etc., respectively. circuits for energizing the relays R|30 and RIM, etc., respectively, in the distributor in the event that the second, third, etc. links, respectively, are idle at this time, these circuits extending from ground, at an amature in the second, third, etc. links, respectively, corresponding to the amature RA220 oi' the hold relay R220 in the first link to the conductors CIII, C|88, etc., respectively. More particularly, the circuit for energizing the relay R|I0 extends from the grounded conductor CI 81, by way of RAI 52, and the winding of RI30 to battery; and the circuit for'energizing the relay RIM extends from the grounded conductor CI88, by way of RAIS3, and the winding of RIM to battery. When thus energized the relays R|30 and R|40 operate to complete, at RA|3| and RAMI, re-

spectively, obvious holding circuits for energizing the respective windings thereof.

Upon operating, the relay RI20 prepares, at RAI2| and RC|22, a circuit traced hereinafter for energizing one of the FG magnets in the iinder switch 5| of the rst link, and interrupts, at RAI 2 and RCI 23, a point in the above-traced circuit for energizing the reset relay R|50 in the distributor |00. Similarly, the relay R|30 prepares,'at RA|32 and RCISS, a point in a circuit extending into the second link by way of the control conductor CIDI and extending from the second link by way of the control conductor CIM for energizing one of the FG magnets in the nder switch 52 of the second link. Similarly, the relay R|40 prepares, at RA|42 and RCI43, a point in a circuit extending into the third link by way oi the control conductor C|92 and extending from the third link by way of the control conductor C|95 for energizing one of the FG" magnets in the finder switch 53 of the third link.

Also, upon operating, the relay R|00 prepares, at RAIDI, at RAI03, at RAIN, etc., circuits for energizing the magnets IFGI, 2FGI, SFGI, etc. respectively, included in the iirst portion of the finder switches 5|, 52, 53, etc. respectively, of the first, second, third, etc. links, respectively. One of the previously mentioned circuits for energizing one of the magnets IFGI, ZFGI, 3FG| or etc.

is completed at this time, depending upon which of the first, second, third or etc. links is assigned to the use of the calling subscriber line, in the event that each of the test relays corresponding to the relay R255 in the iirst link occupies a restored position at this time. 'I'he link which is assigned to the use of the calling subscriber line Il is dependent upon the idle or busy condition of the links, as the distributor |00 is operative to assign the iirst, second, third, etc. links to the use of calling ones of the lines sequentially, In the present instance, it is assumed that the iirst link is idle and that the relay RI20 occupies its operated position, as previously noted. Furthermore, it is noted that the completion of the circuit for energizing one of the FG magnets noted is dependent upon the restored position of the test relays corresponding to the test relay R255 in the iirst link. More particularly, it is noted that this circuit is completed only in the event that each of these test relays occupies a restored position. This arrangement is provided for the purpose of preventing the operation of satana one of the "FG magnets in one of the iinde,`

switches simultaneously with the operation orn one oi' the CG magnets in one o1' the connector switches or one of the L" magnets by the control apparatus associated' with one of the links,

ydue to the fact that such simultaneous operation of the magnets noted would cause improper operation of the cross-bar switch 50 to select a,

called line at this time, as will appear hereina r.

Assuming that each o! the test relays in each of the links occupies a restored position at this time, a circuit is completed for energizing the magnet IFGI by the joint operation of the relays R|00 and RI20. This circuit extends from ground, at RAZ, by way of RC25'I, the chain circuit through the contacts controlled by the test relaysin the other links, CISI, RAI02, RAIZI, RCI22, C|00, RA220, CIN, RAIOI, and the winding of IFGI to battery. When energized over the above-traced circuit the magnet IFGI operates to operate the operating element IFGIS associated therewith, thereby to cause the contact rods of the twenty elementary switches 600 associated with the operating element IFGIS to be operated from their normal positions, as previously explained. Also, the magnet IFGI completes, at IFGAI, a circuit for energizing in series the upper winding of the line relay R|60, and the winding of the magnet LII, this circuit extending from ground, at IFGAI, by way of CIBG, RAIGS, RAIBZ, the upper winding of RISO, CH3, and the winding of LII to battery. When energized over the above-traced circuit the line relay RI50 is retained in its operated position and the magnet LI I is operated. Upon operating, the magnet LII actuates its armature LI IA, thereby to operate the associated operating member LI IS. 'I'his operation of the operating member LIIS is effective to cause the contact strips of the elementary switches 600 associated therewith to be operated away from their normal positions in order to cause the elementary switch 600 illustrated, which is associated with both the operating member LI IS and the operating element IFGIS, to be fully operated. When this elementary switch 500 is fully operated the trunk line |05 extending to the control apparatus 200 is connected to the calling subscriber line I I. More particularly, the contact strips I ILSI IIISZ, and ||LS3 in the fully operated elementary switch B00 illustrated and associated with both the operating element |FG|S and the operating member LI IS engage the contact rods |FGS4, IFGSS, IFGSG, respectively, in this elementary switch. Also, upon operating, the magnet LII interrupts, at ||LA2 and IILCl, and at IILAI, points in the original bridge circuit for energizing the lower winding of the line relay RIEI), and completes, at ||LA2 and IILC3, the circuit for energizing the winding of the cut-off relay Rill?. The latter circuit extends from ground, at II LA2 by Way of IILC3, RAISE, and the winding of Rill! to battery. When energized over the above-traced circuit the cut-oil? relay RII operates to interrupt, at RAIlI and RCII3, a further point in the original bridge circuit for energizing the lower Winding of the line relay RISU, and completes, at RAIN, a holding circuit for energizing the winding thereof, extending from ground, at I ILA2, by way of IILC3, RAIN, and the winding of RI'I0 to battery.

When the calling line is connected to the trunk line |05 extending to the control apparatus 200 associated with the first link, a circuit is completed for energizing the line relay R2I0 included in the control apparatus 200. This circuit extends from ground, at the upper winding of R2I0, by way of the upper winding of R2I0, C262, CI08, IIGSB, IILS3, CIM, the bridge path at the substation A between CIO| and CI80, C|00, IILS2, IFGS5, C|I, 025|, and the lower winding of R2I0 to battery. When energized over the above-traced circuit the relay R2I0 operates to complete, at RA2II and RC2I2. an obvious circuit for energizing the hold relay R220. When thus energized the hold relay R220 operates to interrupt, at RA22I and RC222, a point in a circuit traced hereinafter for energizing the release magnets M306 and M3I6 of the minor switches 300 and 3I0, respectively, to prepare, at RA22I and RC223, a point in a circuit traced hereinafter for energizing the transfer relays R230 and R240, the ring cut-oil relay R210 and the busy relay R280, and to prepare, at RA224, a point in a pulsing circuit traced hereinafter for energizing the rotary magnets M305 and M3I5 of the minor switches 300 and 3I0, respectively. Further the hold relay R220 interrupts, at RA228, a point in vthe previously traced circuit for energizing the magnet IFGI, completes, at RA225 and RA226, a path for applying ground potential to the control conductor CI05 of the trunk line |05, and interrupts, .at RA225 and RC22I, a point in the previously traced circuit for energizing the relay RI20 in the distributor |00.

When the path is completed for applying ground potential to the control conductor CIDE, a holding circuit is completed for energizing the magnet LII and for applying ground potential to the control conductor CI83 of the subscriber line II, this path extending from ground, at RA225, by way of RA225, CI06, IFGSII, IILSI and CI32 to CI83, and from CI83 by way of the winding of LII to battery. Thus, the magnet LII is retained in its operated position, thereby to retain the elementary switch 600 illustrated in its fully operated position. Also this application of ground potential to the control conductor CI83 of the subscriber line II marks the subscriber line II as busy to the connector switches 54, 55, 55, etc., of the iirst, second, third, etc., links having access thereto. When the circuit for energizing the magnet IFGI is interrupted, this magnet restores, thereby to cause the contact rods of each of the elementary switches 500 associated therewith, with the exception of the fully operated elementary switches illustrated, to be returned to their normal positions. Also, upon restoring, the magnet IFGI interrupts, at IFGAI, the previously traced circuit for energizing the upper winding of the line relay RI60 in series with the winding of the magnet LII, thereby to cause the line relay RI50 to restore. Also, when the circuit for energizing the relay RI20 in the distributor |00 is interrupted, the relay RI20 restores, thereby to interrupt, a-t RAIN, a further point in the holding circuit for the winding thereof, to interrupt, at RAI2I and RCI22, a further point in the circuit for energizing the magnet IFGI, and to prepare, at RAI2I and RCI23, a point in the circuit for energizing the FG 'magnets included in the finder switch 52 of the second link. Upon restoring, the line relay RI60 interrupts, at RAI65, a point in the original circuit for energizing the cut-oftrelay RI'I0, interrupts, at RAIGZ and RAIGS, a

further point in the circuit for energizing the upper winding of the line relay RI00 in series with the winding of the magnet LII, prepares, at RAI and RCI, a point in the previously mentioned ground circuit including the control conductors CIOC, CI and C334, and interrupts, at RAISI, the circuit for energizing the relay RI00 in the distributor |00. When the previously mentioned chain circuit including the control conductors CI, CI and C334 is prepared, at RAI and RCI, the circuits ior energizing the upper windings of-the line relays included in the line circuits, individually associated with the` other subscriber lines in the rst group oi' lines, are conditioned to be operated. When the circuit for energizing the winding of the relay RI00 in the distributor |00 is interrupted, the latter relay restores. thereby to interrupt, at RAI02, a point in the previously prepared circuits for 'energizing the FG magnets included in the nder switches of the links, and t'o interrupt, at RAIOI, RAI03, RAI04, etc., points in the previouslyprepared circuits for energizing the magnets IFGI, 2FGI, 3FGI etc., respectively, included in the lirst portions of the finder switches 5I, 52, 53, etc., respectively, of the rst, second, third, etc., links. At this time the distributor |00 is completely released for further use and the second link in the system is assigned to the use of a calling one of the lines due to the fact that the relays RI20 and RI30 therein occupy their restored and operated positions, respectively.

From the foregoing description of the operation of the distributor |00 to cause the finder switch 5I toseize the calling subscriber line II, it will be understood that, in the event the calling subscriber line had been a line in the second group, such, for example, as the line 3| rather than the line II, the line circuit individually associated therewith would have been operated to cause ground potential to be applied to the start conductor CI9`I extending into the distributor |00, whereupon the relay RIIO would have been operated. Upon operating, the relay RI I0 prepares, at RAIN, a point in the previously traced circuits extending into the rst, second, third, etc., links, and prepares, at RAI I3, RAI I2. RAI I I, etc., respectively, circuits for energizing the magnets IFG2, 2FG2, 3FG2, etc., respectively, included in the second portions of the linder switches 5I, 52, 5,3, etc., respectively, of the rst, second, third, etc., links, respectively. 'I'he subsequent operation of the distributor to cause one of these FG magnets to be energized is the same as that previously described, depending upon the one of the links assigned to the use of the calling subscriber line and upon the restored positions of each of the test relays in the ilrst, second, third, etc., links corresponding to the test relay R255 in the ilrst link.

Continuing now with the operation of the control apparatus 200 included in the iirst link to cause the cross-bar/switch 50 to operate and seize the called subscriber line I2, the control apparatus 200 associated with the flrst link is conditioned to be responsive to digits dialed at the substation A associated with the calling subscriber line I I when the ilnder switch 5I is operated to connect the trunk line |05 extending to the control apparatus 200 to the calling scriber line II.

The subscriber at thesubstation A then dials the iirst digit of the directory number of the called subscriber line at the dial mechanism thereat, thereby to transmit a first series of imsubpulses over the loop circuit extending by way of the calling subscriber line between the substation A and the line relay R2|0 included in the control apparatus 200. 'I'he line relay R2|0 follows the impulses transmitted thereto, operating each time this loop circuit is completed and restoring each time this loop circuit is interrupted. Each time the line relay R2|0 operates, it completes, at RA2|| and RC2I2, the previously mentioned circuit for energizing the hold relay R220; and each time the line relay R2|0 restores it completes, at RA2| and RC2 I 3, a circuit for energizing in multiple the winding of the control relay R2|5 and the rotary magnet M305 of the minor switch 300.

This circuit extends from ground, at RA2II,

by way of RC2I3 to RA224, one branch extend-l ing from RA224 by way of the winding of R2|5 to battery, and the other branch of this circuit extending from RA224 by way of RA235, RC231, C2l8, and the winding of M305 to battery. Each time the above-traced circuit is completed the control relay R2|5 is energized and the rotary magnet M305 is energized, the successive energization of the rotary magnet M305 being effected to rotate the wipers 30| and 303 of the minor switch 300 step by step in a clockwise direction and into engagement with the successive contacts in the associated contact banks 302 and 304, respectively. Upon operating, the control relay R2|5 completes, at RA2l6, a circuit for energizing the lower winding of the transfer relay R230, this circuit extending from ground, at RA2|6, by way of RA23I, RC232, RA242, and the lower winding of R230 to battery. When energized over the above-traced circuit the transfer relay R230 partially operates to close the X contacts associated with RA234, thereby to complete a path for short-circuiting the upper winding thereof, this path extending from ground, at RA2|6, by way of RA23|, RC232, RA242, the upper winding of R230, RA234, RA24I, C260, RC223 and RA22| to ground. Due to the facts that the hold relay R220 and the control relay R2|5 are of the slow-to-release type and that the above-mentioned circuits for energizing these relays are alternately completed these relays remain in their operated positions during the series of impulses comprising the iirst digit. When the wipers 30| and 303 of the minor switch 300 are rotated away from their normal positions, the switch springs S301 are actuated into engagement, thereby to prepare a circuit traced hereinafter for energizing the release magnet M306 of the minor switch 300.

At the conclusion of the iirst digit, the wipers 30| and 303 of the minor switch 300 engage odd or even contacts in the associated contact banks 302 and 304, respectively, depending upon the number of impulses comprising the first digit. In the event the first digit dialed comprises one or two impulses, the wiper 30| engages the rst or second contacts, respectively,- in the associated contact bank 302, which contacts are multipled together and terminate the control conductor C320 extending to the CG magnet included in the first portion of the connector switch 56 ofthe first link. Similarly, should the first digit comprise three or four impulses, the wiper 30| engages the third or fourth contacts, respectively, in the associated contact bank 302, which contacts are multipled together and connected to a control conductor extending to the CG magnet included in the second portion ofthe 'connector estarse Y switch se of the mi unk. Likewise, it wm be understood that, if the ilrst digit comprises 5, 0 or l, 3 or 3, 0, the wiper 3l|will engage a corresponding contact in the associated contact bank 303, thereby respectively to prepare a circuit for energizing the CG" magnet in the third, fourth or fifth portions, respectively, of the connector switch 56 ot the nrst link. Also, it will be noted that, in the event the rst digit comprises an odd number of impulses, the wiper 333 engages a corresponding odd contact in the associated contact bank 304 multipled to the wiper 3|| of the minorswitch 3|0; and, in the event the first digit comprises an even number of impulses, the wiper 303 engages a corresponding even contact in the associated contact bank 304 multipled vto the wiper 2|3 of the minor switch 3|0. In the present instance, in view of the fact that the called subscriber line |2 is included in the ilrst ten line portion of the iirst twenty line group, the irst digit dialed necessarily comprises a single impulse. Accordingly, the wiper 30| of the minor switch 300 engages the nrst contact in the associated contact bank 302, thereby to prepare a circuit traced hereinafter for energizing the magnet |CG| in the iirst portion of the connector switch 53 of the iirst link; and the wiper 303 engages the first contact in the associated contact bank 304, thereby to prepare a circuit traced hereinafter for energizing one of the "L" magnets included in the ilrst ten line portion of the iirst twenty line group by way of the wiper 3| of the minor switch 3|0. On the other hand, if the wiper 303 had engaged an even contact in the associated contact bank 304 instead of an odd contact therein, a circuit would have been prepared for energizing one of the L magnets associated with a line in the second ten line portion of the first twenty line group by way of the wiper 3|3 of the minor switch 3|0.

At the conclusion of t'he iirst digit dialed the line relay R2|0 reoperates, thereby to complete the previously mentioned circuit for energizing the hold relay R220 and to interrupt the previously traced circuit for energizing in multiple the winding of the control relay R2I5, and the winding of the rotary magnet M305 of the minor switch 300, in order to retain the hold relay R220 in its operated position, to arrest further operation of the minor switch 300, and to cause the control relay R2|5 to restore shortly thereafter. Upon restoring, the control relay R2|5 interrupts, at RA2|6a point in the previously traced path for shortcircuiting the upper winding of the transfer relay R230, whereby a circuit is completed for energizing the upper and lower windings of the transfer relay R230 in series, this circuit extending from ground, at RA22I, by way of RC223, C280, RA24|, RA234, and the upper and lower windings of R230 to battery. When the upper and lower windings of the transfer relay R230 are thus energized in series, this transfer relay fully operates, thereby to interrupt, at RA23| and RC232, a further point in the path for short-circuiting the upper winding thereof, to prepare, at RA23| and RC233, a point in a circuit traced hereinafter for energizing in multiple the lower winding of the transfer relay R240, and the winding of the control relay R250, to interrupt, at RA235 and RA231, a further point in the circuit for energizing the rotary magnet M305 of the minor switch 300, to prepare, at RA23E and RC2, a point in a circuit traced hereinafter for energizing the rotary magansa-us with the first link. The line relay R2I0 follows this series of impulses, as previously explained. Each time the line relay R2I0-operates it completes, at RA2II and RCZIZ, the previously mentioned circuit for energizing the `hold relay R220; and each time the line relay R2I0 restores it completes, at RAZII and RCZIJ, a circuit for energizing in multiplethe winding of the control relay RZIB, and the winding of the rotary magnet M3I0 of the minor switch IIO. This circuit extends from ground, at RAZI I, by way of RC2I3 to RAZZ4, one branch of this circuit extending from RA224 by way of the winding of RZII to battery, and the other branch of this circuit extending from RA224 by way of RAZ, RC2, CZI'I, and the winding of MMU to battery. Each time the above-traced circuit is completed, the winding of the control relay RZII and the winding of the rotary magnet MMS are energized, thereby to cause the control relay RZII to operate and remain operated during the second series of impulses, and to cause the rotary magnet M3I0 to operate a number of times corresponding to the number of impulses comprising the second digit.

Upon reoperating, the control relay RZII completes, at RAZIB, the previously mentioned circuit for energizing in multiple the lower winding of the transfer relay R240 and the winding of the control relay R250, this circuit extending from ground, at RAZIG, by way of RAZSI to RC2, one branch of this circuit extending from RC233 by way of RAZ, and the lower winding of R240 to battery, and the other branch of this circuit extending from RC233 by way of the winding of R250 to battery. When energized over the above-traced circuit the transfer relay R240 operates to close the X" contacts associated with the armature RAZ, -thereby to complete a path for short-circuiting the upper winding of R240, this path extendin'g from ground, at RA2IB, by way of RAZII, RC2, RAZ, the upper winding of R240, RAZ, C260, RCZZI, and RAZZI to ground. When the control relay R200 is energized over theabove-traced circuit it operates, thereby to prepare, at RAZSI, a point in the previously mentioned circuit for energizing the test relay R255, and to interrupt, at RAZlZ, a point in a circuit traced hereinafter for returning busy tone current over the loop circuit including the calling subscriber line II extending to the substation A.

At the conclusion of the second digit, the wipers 3| I and 3l: engage contacts in the associated contact banks cl2 and 0M, respectively; corresponding to the number of impulses comprising the second digit. The engagement of the wiper 3| I arid one of the contactsin the associated contact bank 3l 2 prepares apoint in a circuit for energizing one of the L magnets in the connector switch 50 and associated with a subscriber line in the flrstyten line portion of the previously selected twenty line group in the system; andthe engagement of the wiper BIB and one of the contacts in the associated contact bank 0I'4 prepares a point 75 inacircuitfor energlzingoneofthel.ma8nltl in the connector switch Il andassociatedwith a subscriberiine in the second ten lineporticnof the previously selected twenty line group ln the system. In'the present instance, the called subscriberline IZisthesecondlineintherstten line portion of the first twenty line will in the system. Accordingly. the second digit dialed comprises two impulses, and a circuit is prepared for energizing the vidually associated therewith and the second contact in the associated contact bank SI2 of the minor switch lll, the path prepared at the wiper M3 and second contact in the associated contact bank 0I4 of the minor switch 3I0 being open-circulted at the contact bank 004 of the minor switch 000 due to the fact that the first digit dialed, the No. 1, comprised an odd number of impulses.

At the conclusion of the second digit dialed, the line relay R2I0 in the control apparatus 200 .reoperates. thereby to complete the previously mentioned circuit for energizing the hold relay R220, and to interrupt the previously traced circuit for energizing in multiple the winding of the control relay R2 I l, and the winding of the rotary magnet MSI! of the minor switch III in order to retain the hold relay R220 in its operated position to arrest further operation of the minor switch M0, and to cause the control relay RZIS to restore shortly thereafter. Upon restoring, the control relay R2Il interrupts, at RAZII, the previously traced circuit for energizing the winding of the control relay R250 and the path for short-circuiting the upper winding of the transfer relay R240, whereupon a circuit is completed for energizing in series the upper and lower windings of the transfer relay R240. The latter circuit extends from ground. at RAZZI, by way of RC220, C200, RAZ, and the upper and lower windings of R240 to battery. The transfer relay R240 immediately operstes fully when it is energized over the abovetraced circuit, and the control relay R200, being of the slow-to-release type. does not restore until a predetermined time interval elapses after the circuit for energizing the winding thereof is interrupted. Upon fully operating, the transfer relay R240 interrupts, at RA24I the circuit for energizing in series the upper and lower windings of the transfer relay R200, thereby to cause the latter transfer relay to restore. Also the transfer relay R240 prepares,` at RAZ, a point in the previously mentioned circuit for energizing the test relay R205, and prepares, at RAZ, a point in the previously mentioned circuit for returning busy tone current over the loop circuit extending by way of the calling subscriber line II to the substation A. Upon` restoring, the transfer relay R220 completes, at RAZ, the previously mentioned circuit`for energizing the test relay R200, this circuit extending from ground, at RAZ, by way of RC2, C200, RAZ, RAZ, RAZSI, and the winding of R2 00 to battery.

When energized over the above-traced circuit the test relay R200 operates to interrupt, at RAZ and RC2 51, the previously traced path for applying ground potential to the control conductor CII'I, thereby to prevent the operation of other of the FG magnets in the finder switches 02, l0, etc., of the second, third, etc., links prior to the restoration of the test relay R250.' Further, the test relay R255 completes, at RAZ and RC250, the previously mentioned circuit for energizingfthe magnet ICGI in the rst portion of the connector switch 56 of the ilrst link, this cirwinding of the magnet LII indiat the wiper III 1 2 cuit extending i'rom ground, at RA2I8, by way of RC258, C2, the wiper 30| and first contact in the associated contact bank 302 of the minor switch 308, C820, and the winding of ICGI to battery. When energized over the above-traced circuit the magnet ICGI operates, thereby to operate the operating element ICGIS associated therewith. This operation of the operating element ICGIS operates away from their normal positions the contact rods of the twenty elementary switches 800 associated therewith and included in the rst portion of the connector switch 50 of vthe first link. Also, upon operating, the magnet ICGI prepares, at ICGAI, ICGA2, ICGA3, ICGAI, ICGA5, etc., circuits for testing the idle or busy conditions oi.' the subscriber lines 22, 2i, I3, I2, II, etc., included in the iirst group of twenty lines. More specifically, the magnet ICGI prepares, at ICGA4, a circuit traced hereinafter for testing the idle or busy condition oi the called subscriber line I2. Also, upon operating, the test relay R255 completes, at RA258, the circuit for testing the idle or busy condition of the called subscriber line. More specifically, the test relay R255 completes, at RA259, the circuit for testing the idle or busy condition of the called subscriber line I2, this circuit extending from ground at the lower winding of the busy relay R280, by way of the lower winding of R280, RA259, C2I5, the wiper 303 and first contact in the associated contact bank 30| of the minor switch 300, the wiper 3II and second contact in the associated contact bank 3I2 of the minor switch 3|0, C322, ICGA4 and C321, to the control conductor C332 of the called subscriber line I2.

The subsequent operation of the control apparatus 200 associated with the ilrst link depends upon the idle or busy condition of the called subscriber line i2. In theevent the called subscribed line I2 is busy, ground potential appears upon the control conductor C332 thereof; and on the other hand, in the event the called subscriber line I2 is idle, battery potential appears upon the control conductor C332 thereof. Assuming that the called subscriber line I2 is busy, ground potential appears upon the control conductor thereof and the lower Winding of the busy relay R280 is short-circuited in an obvious manner over the above-traced test circuit. Thus,

the busy relay R280 does not operate, and shortly after the test relay'R255 operates the control relay R250 restores. Upon restoring, the control relay R250 interrupts, at R.A25I, the circuit for energizing the test relay R255, thereby to cause the latter relay to restore. Upon restoring, the test relay R255 recompletes, at RA256 and RC251, the previously traced path for applying ground. potential to the control conductor Cisl includedfinlthe chain circuit extending through the contacts controlled bythe test rela-ys in the other links corresponding to the test relay R255, and interrupts, at RA255 and RC258, the previously traced circuit for energizing the magnet ICGI, thereby to cause the latter magnet to restore. Also, upon restoring` the test relay R255 interrupts, at RA259, a point in the previously traced circuit for testing the idle or busy condition of the called subscriber line I2. Also, upon restoring, the control relay R250 completes, at RA252, a circuit for returning busy tone current over the -loop circuit including the calling subscriber line II extending to the substation A, this circuit extending from the ungrounded terminal of the grounded winding of a source of busy tone current by way of the busy tone con a,ass,74s f amor cm, mais, mm, nom, ruim, can,

C2I8, and the condenser 248 to the line con ductor CI08 of the trunk line |05, and from ground, at the lower winding oi' the back bridge relay R250, by way ot .the lower Winding of R250, C250, C2I2, and the condenser 241 to the line conductor CIOI of the trunk line |05, the line conductors CI08 and CI0l of the trunk line |05 being connected, respectively, by way of IFGS5, IILS3, and IFGS5. IIL`S2, to the line conductors CI8| and CI82, respectively, of the calling subscriber line II, and the receiver of .the telephone instrument at the substation A being included in a bridge circuit across the line conductors CI8i and CI80 of the calling subscriber line II. The resulting busy tone produced in the receiver of the telephone instrument at the substation A indicates to the subscriber thereat that the desired connection cannot immediately be had due to the busy condition o! the called subscriber line I2. The subscriber atthe substation A then replaces the receiver of the telephone instrument thereat upon its hook, thereby to cause lthe portions of the crossbar switch 50 included in the finder -and connector switches 5I and 55, respectively, of the ilrst link and the control apparatus 200 associated with the ilrst link to be released. The exact manner in which these operated pieces of apparatus are released is described in detail hereinafter.

Assuming that the called subscriber line i 2 is idle when the test relay R255 is operated, battery potential appears upon .the control conductor C332 thereof, as previously noted, this battery potential being derived at one terminal of the winding of the magnet Li2.and extending therefrom by way of .the winding of LI2 to the control conductor C332. Under these conditions, when the previously traced test circuit is completed, at RA250, upon the operation of the test relay R255, a circuit is completed for energizing in series the lower winding of the busy relay R280 and the winding of the magnet LI2. 'I'his circuit extends from ground at the lower winding of R280, by Way of the lower winding of R280,

RA259, C2I6, the wiper 303 and ilrst contact in the associated contact bank 804 of the minor switch 300, the wiper 3II and second contact in the associated'contact bank 3I2 of the minor switch 2I0, C822, ICGA4, C321, C332, and the winding of LI2 to battery. When energized over the above-traced circuit, the busy relay R280 partially operates, thereby to close, at RA288, the X" contact associated therewith, and the magnet LI2 fully operates. When the busy relay R280 partially operates to close .the X" contact associated with RA289, a holding circuit is completed for energizing the upper winding of R280, this circuit extending from ground, at RA22I, by way of RC223, C250, RA289, and the upper winding of R280 to battery. When the above-traced holding circuit is completed for energizing the upper winding of the busy relay R280, this relay fully operates, thereby to interrupt, at RA28I and RC283, a point in the previously traced circuit ior returning busy tone current over the loop circuit including the calling subscriber line II extending to the substation A, and to complete, at RA28I and RC282, av circuit traced hereinafter for returning ring-back-tone current over the loop circuit including the calling subscriber line II extending to the substation A.

Upon operating, the magnet LI 2 actuates its associated armature LI2A, thereby to operate the operating member LI2S associated therewith.

switches 530 associated therewith. Iv-Iowever,-

illustrated elementary switch 000 asso;`

only the ciated with both the operating element ICGIS and the operating member LI2S is fully operated, thereby to cause the trunk line 252, extending from the control apparatus 200 associated with the first link, to seize the called subscriber line I2. More particularly, the contact rods ICGS4, |CGS5 and ICGSI engage the contact strips |2LSI, |2LS2 and I2LS3, respectively, in the illustrated elementary switch 500.

Also, upon opera the busy relay R280 compietes, at RA204 and RA235, a holding circuit for energizing the magnet LI2, this circuit extending from ground, at RA205, by way of RAZ, C253, ICGSI, |2LSI, C332, and the winding or LI2 to battery. to apply ground ductor C332, thereby to mark the subscriber line I2 as busy to the connector switches 55, 54 of the second, third, etc., links, respectively, having access thereto. Furthermore, the busy relay R200 interrupts, at RA205 and RC205., a point in the previously traced circuit for energizing the test relay R255, thereby to cause the latter relay to restore prior to the restoration of the control relay R250, which latter relay restores shortly after the operation of the busy relay R280. Upon restoring, the te'st relay R255 interrupts, at RA255 and RC255, the previously traced circuit for energizing the magnet ICGI, and completes, at RA250 and RC251, the previously traced path for applying ground potential to the control conductor CI51. Finally, the control relay R255 interrupts, at RA255, a point in the original circuit ior energizing the-lower winding of the busy relay R200 in series with the winding oi the magnet LI2.

When the circuit for energizing the magnet ICGI is interrupted the latter magnet restores, thereby to cause the contact rods of the twenty elementary switches 530 associated therewith, with the exception of the fully operated elementary switch 500 illustrated, to be returned to their normal positions. The fully operated elementary switch 000 illustrated is retained in Also, this circuit is effective.: potential to the control con"'- its operated position due to the fact that the magnet LI2 occupies its operated position, the magnet LI! being energized at this time by way of the previously traced holding circuit for energizing the winding thereof, and the original circuit for energizing the winding thereof being interrupted, as previously noted. Also, when the magnet LIZ operates it interrupts, at I2LAI and at |2LA2 and I2IA'J4, points in the bridge circuit for energizing the lower winding of the line relay R350 included in the line circuit 300 individually associated with the subscriber line I2, thereby to prevent the line relay R350 from rbeing operated when the call is answered at the substation B by the removal oiA the receiver of the telephone instrument thereat from its hook.

Finally, when the busy relay R280 operates it completes, at RA231 and RA205, points in a circuit for projecting ringing current over the called subscriber line I2 extending to the substation B. The circuit for projecting ringing current over the called subscriber line I2 extending to the substation B extends from ground, at RC215, by way of RA215 and RA200, to the line conductor C255 of the trunk line 252, and from the ungrounded terminal of a grounded winding of a source o ringing current by way 'of the ringing conductor C253, the lower winding of the ring cut-ofi relay R213, RA212, RC2, RA213 and RA201, to the line conductor C254 of the trunk line252, the line conductors C255 and C254 of the trunk line 252 being respectively connected by way of ICGSB, |2183 and ICGS5, I2LS2, to the line conductors C33I and C330. respectively, oi the called subscriber line I2, and the ringer at the substation B being included in a circuit extending between the line conductors C330 and C33I. When the above-traced circuit is completed the ringer at the substation B is operated, thereby to indicate to the subscriber thereat that the substation B is a called substation. Also a circuit is completed at this time for returning ring-back-tone current over the loop circuitincluding the calling subscriber line I| extending to the substation A, as previously noted. This circuit extends from 'ground at one terminal of the lower winding of the back bridge relay R250 by way oi the lower winding of R260, C258, C2I2, and the condenser 241, to the line conductor CI01 of .the trunk line |05, and from the source of potential-appearing upon the ringing conductor C253, as previously noted, by way ofthe lower winding of the ring cut-oi! relay R210, RA212, the condenser 249, RC282, RA28I, C251, C2I3, and the -condenser 240 to the line conductor C|08 of the trunk line |05, the line conductors CI01 and C|05 of the trunk line |05 being connected to the line conductors C|00 and CI8I, `respectively, of the calling subscriber line II, and the receiver of the telephone instrument at the substation A being included in a bridge circuit extending between the line conductors C| and CI8I of the calling subscriber line II, as previously noted. This ring-back-tone current returned over the loop circuit including the calling subscriber line II and extending to the substation A causes the receiver thereat to be actuated, thereby to produce ring-back-tone therein in order to indicate to the subscriber at the substation A that the ringer at the substation B associated with the called subscriber line I2 is being actuated.

The call is answered at the substation B associated with the called subscriber line I2 when the receiver of the telephone instrument thereat is removed from its hook, thereby to complete a circuit, which is substantially identical Ato the previously traced circuit for projecting ringing current over the called subscriber line I2, for energizing the lower Winding of the ring cut-off relay R210. When the lower winding of the ring cut-of! relay R210 is thus energized, this relay partially operates to close the X contacts associated with RA21I in order to complete a holding circuit for energizing the upper winding of R210. The latter circuit extends from ground, at RA22 I, by way of RC223, C250, RA21I, and the upper winding of R210 to battery. When energized over the above-traced holding circuit the ring cut-off relay R210 fully operates, thereby to interrupt, at RA212, at RA213 and 13.0215, and at RA2'I5 and RC215, points in the circuit for projecting ringing current over the called subscriber line I2, to interrupt, at RA212, a point in the circuit for returning ring-back-tone current over .the loop circuit including the calling subscriber line II extending to the substation A, and to complete, at RA213 and RC2, and at RA215 and RC211, a loop circuit between the back bridge relay R250 and the subscriber substation B. This loop circuit extending between the back bridge relay R250 and the substation B extends from ground, at one terminal of the lower winding of R260 by way of the lower winding o! R260, C256, RC214, RAZ'I3 and RAZ81 to the line conductor CZ54 of the trunk line 252, and from battery, at one terminal of the upper winding of f ergized over the above-traced loop circuit the back bridge relay R260 operates to complete, at RAZSI, an obvious multiple path for applying ground` potential to the control conductor C260, thereby to complete multiple holding circuits for the transfer relay R240, the ring cut-oil relay R210, and-the busy relay R280. At this time, talking battery is supplied to the loop circuit including 'the calling subscriber line II extending to the substation A from ground and battery potentials appearing at the line relay RZIO; and talking battery is supplied to the loop circuit including the called subscriber line I2 extending to the substation B from ground and battery potentials appearing at the back bridge relay R260. Furthermore, the loop circuit including the calling subscriber line I I extending to the substation A is connected to the loop circuit including the called subscriber line I2 extending to the substation B by way of the voice frequency condensers 241 and 246. More specically, the line conductor C|01 of the trunk line I05 is connected by way of the condenser 241, CZIZ, RC214, RA213 and RA201, to the line conductor C254 of the trunk line 252: and the line conductor CI06 of the trunk line I is connected by way of the condenser 246, C2I3, RCZ11, RAZ16 and RAZBB to the line conductor C255 of the trunk line 252. At this time, the substations A and B associated, respectively, with the subscriber lines I I and I2 are interconnected by way of the first link comprising the first portion of the iinder switch 5I and the iirst portion of the connector switch 56, and the control apparatus 200 associated with the rst link for two-way communication therebetween.

The release of -this established connection is primarily under the control of the calling party. When the subscriber at the substation B replaces the receiver of the telephone instrument thereat upon its hook, the loop circuit extending between the back bridge relay R260 and the substation .B is interrupted, thereby to cause the back bridge relay R260 to restore. Upon restoring, the back bridge relay R260 interrupts, at RAZSI, one of the multiple paths ior applying ground potential to the control conductor C260. However. the holding circuits for thetransfer relay R240, the. ring cut-oii' relay R210 and the busy relay R280 are retained completed at this time due to the operated condition of the hold relay R220. Accordingly, the finder switch 5I and the connector switch 56 included in the first link are retained in their operated positions at this time, and the subscriber line I2 is still marked as busy to the connector switches of the links having access thereto until the connector switch 56 is released.

When the subscriber at the substation A replaces the receiver of the telephone instrument thercat upon its hook, the loop circuit extending between the line relay R2I0 and the substation A is interrupted, thereby to cause the latter relay to restore. Upon restoring, the line relay RZIO interrupts, at RAZI I and RCZIZ, the previously mentioned circuit for energizing the hold relay R220. VShortly thereafter the hold relay R220, being of the slow-to-release type, restores to interrupt, at RAZZI and RCZZ3, the holding circuits for energizing the transfer relay R240, the ring cut-otI relay R210 and the busy relay R280, thereby to cause the latter relays to restore. Also, the hold relay R220 completes, at RAZZI and RCZZZ, a circuit for energizing in multiple the release magnets M306 and M3I6 of the minor switches 300 and 3| 0, respectively, this circuit extending from ground, at RAZZI and RCZZZ, to the control conductor CZI5, one branch of this circuit extending from C2I5 by way of the switch springs S301, and the winding of M306 to battery, and the other branch of this circuit extending from the control conductor C2I5 by way of the switch springs S3I1 and the winding of M3I6 to battery. When energized over the above-traced circuit the release magnet M30-6 operates, thereby to release the wipers 30| and 303 of .the minor switch 300, and to cause these wipers to be returned to their normal positions. Similarly, when the release magnet M3I5 is energized it operates, thereby to release the wipers 3H and 3I3 of the minor switch 3I0 and to cause these wipers to be returned to their normal positions. When the wipers 30| and 303 oi' the minor switch 300 are returned to their normal positions, the switch springs S301 are actuated into disengagement, thereby to interrupt the branch circuit for energizing the release magnet M306; and when the wipers 3II and 3| 3 of the minor switch 3I0 are returned to their normal positions, the switch springs S3I1 are actuated into disengagement, thereby to interrupt the branch circuit for energizing the release magnet M3I 6.

Upon restoring, the transfer relay R240 interrupts, at RAZ45, a further point in the circuit for energizing the test relay R255, interrupts, at RA246, a further point in the circuit for returning busy tone current over the loop circuit including the calling line, interrupts, at RAZ44, a further point in the holding circuit for energizing the upper and lower windings thereo i', prepares, at RAZ43, a point in the circuit for energizing the lower winding thereof, prepares, at RA24Z, a point in the circuit for energizing the lower winding of the transfer relay R230, and prepares, at RA24 I, a point in the holding circuit for energizing the upper and lower windings of the transfer relay R230. Upon restoring, the ring cut-off relay R210 interrupts, at RAZ1I, a further point in the holding circuit for energizing the upper winding thereof, prepares, at RA212, a point in the circuit for returning ringback-tone current over the calling subscriber line, interrupts, at RAZ'I3 and RCZ14, and at RAZ16 and RCZ11, further points in the loop circuit including the called subscriber line IZ extending to the substation B, and prepares, at RAZ13 and RCZ15,' and at RA216 and RCZI8, points in the circuit for projecting ringing current over the called subscriber line. When the busy relay R200 restores it interrupts, at RAZ, a further point in the holding circuit for ener.. gizing the' upper winding thereof, interrupts, at RA28I and RC282, a point in the circuit for restores, thereby to cause both the contact strips and contact rods of the fully operated elementary switch 600 illustrated to be returned to their normal positions. Further, the magnet L|2 prepares, at |2LAI and at I2LA2 and |2LC4, points in the bridge circuit for energizing the lower -winding of the line relay R350 included in the line circuit 300 individually associated with the subscriber line |2. At this time, the connector switch $8 of the iirst link is completely released, and battery potential at the winding of the magnet LIZ appears upon the control conductor C332 of the subscriber line I2, thereby to mark the subscriber line I2 as idle to the connector switches of the links having access thereto.

Also, when the hold rel-ay R220 restores it interrupts, at RA224, a point in the pulsing circuits for energizing the rotary magnets M305 and MM of the minor switches 300 and 3|0, re-` spectively, prepares, at RA226 and RC221, a point in the circuit for energizing the relay R|20 in the distributor |00, thereby to condition the latter relay to be operated in order to assign the iirst link to the use of a calling line when the reset relay RI50 in the distributor |00 is again operated. Finally, the hold relay R220 interrupts, at RA225 and RA226, a point in the holding circuit for energizing the winding of the magnet LII, thereby to cause the latter magnet to restore. Upon restoring, the magnet LII causes bothtthe contact strips and contact rods of the illustrated elementary switch 600 to be returned to their normal positions. Further, the magnet LII interrupts, at IILA2 and IILC3, a point in the holding circuit for energizing the cut-off relay RII0, and prepares, at I|LA2 and IILC4, and at IILAI, an alternative circuit for reenergizing the cut-oir relay RI'I0 in the event another call is initiated at the subscriber substation A prior to the restoration of the slow-to-release cut-ofi' re. lay R|10 and to the complete release of the ilnder switch 5I of the iirst link. In the event that a call is not immediately initiated at the substation Athe above-mentioned alternative circuit for energizing the winding of the cut-oit relay R|10 is not completed, and shortly thereafter the cut-oil relay RI10 restores to interrupt, at RAIN and RCI'I I., a point in the previously mentioned alternative circuit, to interrupt, at RAIN, a further point in the `holding circuit for energizing the winding thereof, and to prepare, at RA|1| and RCI13, the bridge circuit for energizing the lower winding of the line relay RISO included in the line circuit |80 individually associated with the subscriber line At this time, the finder switch 5| of thev iirst link iscompletely released, and battery potential derived at the winding of the magnet LI I appears upon the. control conductor C|83 of the subscriber line II, thereby to mark the subscriber line II as idle to the connector switches of the links having access thereto.

si aus ame, bouine. ander, nach', u ,and the connectorswitch l0 of the first link, and the control apparatus 200 vassociatedwiththe rst link, are completely released for turther'usaand the first link will be reassigned to the useof a calling line when the reset relay R|l0 in .the distributor |00 isagain operated. Furthermore, each of the subscriber lines I and' I2 are marked as idle to the connector switches of the links having access thereto and may be seized upon a call being routed thereto. Furthermore, the line circuits lso sind ssnindividuauy associated with the subscriber lines and I2, respectively, are conditioned to be operative in response tothe initiation of a call thereat, thereby to cause the distributor |00 .to operate and assign an idle one' of the links to the use of the calling line.

From the foregoing description of the operation of the system incident to the extension of a call from the subscriber substation A to the subscriber substation B, it will be understood that a call from any one of the subscriber substations is initiated and extended to any one of the other substations, in a manner similar to that described. q

While there have been described what are at present considered to be the preferred embodiments of the invention, it will be understood that various modications may .be made therein, and it is intended to cover in the appended claims all such modiilcations as fall within the true spirit and scope of the invention.

What is claimed is:

1. Ina signaling system, a group of signal lines, unitary switching apparatus including a finder switch and a connector switch, each of said switches having access to each of saidnsignal lines, a rst operating element associated with said finder switch, a second operating element associated with said connector switch, a plurality of operating members, each of said operating members being associated with only one of said signal lines, a link circuit, means controlled by the joint operations of said ilrst operating element and one of said operating members i'or causing said finder switch to seize in said group of signal lines the signal line corresponding to said one operating member and to connect the seized signal line to said link circuit, impulse responsive means included in said link circuit for selecting any one of said signal lines, means included in said link circuit for causing said second operating element to be operated and for causing the idle or busy condition of the selected signal line to be tested, means included in said link circuit and controlled by said last-mentioned means only in the event the selected signal line is tested idle for causing the one of said operating members corresponding to the selected signal line to be operated, and means controlled by the joint operations of said second operating element and said one operating member for causing said connector switch to seize insaid group of signal lines the selected signal line and to connect the seized signal line to said link circuit.

2. In a signaling system, a group of signal lines, unitary switching apparatus including va number of vfinder switches and a number of connector l switches, each of said switches having access to each of said signal lines, a plurality of rst operating elements, each of said first operating elements being associated with only one of said finder switches, a plurality of second operating elements, each of said second operating elements being associated with only one of said connector switches, a plurality of operating members, each 

